Crane control device

ABSTRACT

An object of this invention is to improve safety in a crane. A boom control signal αr and a winch control signal βr are simultaneously outputted to, respectively, a boom drive portion and a winch drive portion of a driving portion 30 for obtaining, respectively, target values Xr, Yr, with current working radius X and lift Y that vary according to the flexure of boom 4 as feedback amounts, thereby a boom hoisting angle and a rope length being controlled simultaneously.

TECHNICAL FIELD

The present invention relates to a device for controlling the boomhoisting angle and the length of a wind-up rope such that the workingradius of the crane or its lift have desired fixed values.

BACKGROUND ART

When a crane is performing a so-called ground-departing operation, it isdesirable that the crane is operated such that the working radiusindicating the horizontal distance from the rotation center of the craneto the tip of the boom is a desired fixed value.

However, when departing from the ground, the load acting on the boomincreases as the hook on which the load is suspended is raised, causingthe boom to flex and thereby increasing the working radius. Conversely,when performing an operation such as pouring fresh concrete, thesuspended load decreases, thus decreasing the boom load and sodecreasing the working radius.

Accordingly, when performing operations in which the flexure of the boomfluctuates as described above, the exercise of control such as tomaintain the working radius at a fixed value is desirable from thestandpoint of increasing ease of working by improving the accuracy oftracking and also from the standpoint of improving safety by preventingaccidents involving contact due to flow of the load.

In some cases, cranes are used to perform horizontal movement operationsin which the suspended load is shifted in the horizontal direction whilemaintaining the lift indicating the vertical distance from the ground tothe hook at a fixed value.

In such cases also, the amount of boom flexure fluctuates with thehorizontal movement of the suspended load, so exercise of control suchas to keep the lift fixed irrespective of such fluctuations in theflexure of the boom is desirable both to improve ease of working asmentioned above and to improve safety.

Conventionally therefore arrangements have been made to compensate forfluctuation in the working radius produced by fluctuation in boomflexure by calculating the amount of flexure produced in the boom and byvarying the boom hoisting angle in accordance with the results of thiscalculation (Japanese Patent Publication Sho.59-26599, Laid-OpenJapanese Patent Application Hei. 1-256496, and Laid-Open Japanese PatentApplication Hei.3-284598, etc).

However, although the prior art, in which only the boom hoisting anglewas changed in order to remove fluctuations of the working radius, didindeed succeed in removing fluctuations of the working radius itself ittended to produce concurrent fluctuations in lift, sometimes resultingin the dangerous condition that the suspended load might spring upabruptly in combination with raising of the boom.

Also, similar problems regarding safety were produced when the prior artwas applied to performing operations in which the lift must be kept at afixed value.

The present invention was made after considering the abovecircumstances, and its object is to perform in a safe manner anoperation that advances by varying the lift while keeping the workingradius constant or an operation that advances by varying the workingradius while keeping the lift constant.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention comprises boom drive means forchanging a boom hoisting angle in response to an input driveinstruction; winch drive means for changing a rope length of the wind-uprope from a tip of the boom to a hook in response to the input driveinstruction; and control means for outputting drive instructionsrespectively to the boom drive means and winch drive means such as toeffect a prescribed operation in which a lift, indicating the verticaldistance from the ground to the hook, is varied, while maintaining theworking radius, indicating the horizontal distance from the rotationcenter of the crane to the boom tip, at a fixed value.

Also, the present invention comprises boom drive means for changing theboom hoisting angle in response to an input drive instruction; winchdrive means for changing the rope length of the wind-up rope from theboom tip to the hook in response to an input drive instruction; andcontrol means for outputting drive instructions respectively to the boomdrive means and winch drive means such as to perform a prescribedoperation by varying the working radius indicating the horizontaldistance from the rotation center of the crane to the boom tip whilemaintaining the lift indicating the vertical distance from the ground tothe hook at a fixed value.

With such a construction, according to the present invention, as shownin FIG. 1, the hoisting angle α of boom 4 is varied in response to adrive instruction αr that is input to boom drive means 30.

In contrast, rope length β of the wind-up rope 8 from the boom tip 4a tohook 9 is varied in response to drive instruction βr that is input towinch drive means 30.

Control means 20 outputs drive instructions αr, βr to the boom drivemeans 30 and winch drive means 30 such as to perform a prescribedoperation while maintaining the working radius X indicating thehorizontal distance from the rotation center of the crane to the boomtip 4a at a fixed value, and varying the lift Y indicating the verticaldistance from the ground to hook 9.

Alternatively, control means 20 outputs drive instructions αr, βr to theboom drive means 30 and winch drive means 30 such as to perform aprescribed operation while maintaining lift Y at a fixed value andchanging the working radius X.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the overall layout of an embodiment ofa crane control device according to the present invention;

FIG. 2 is a view showing the control block diagram of the embodiment;and

FIG. 3 is a side view showing the layout of a crane employed in theembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a crane control device according to the presentinvention is described below with reference to the drawings.

FIG. 1 is a block diagram illustrating the overall layout of theembodiment; in broad terms it consists of a sensor unit 15 arranged onthe crane and comprising sensors 10 etc that detect the amounts ofconditions necessary for control, a control unit 20 that inputs thedetected values of sensor unit 15 and that generates control signals αr,βr for drive control of the boom 4 and winch, and a drive unit 30 thatinputs control signals αr, βr that are output from control unit 20 andthat drives by hydraulic pressure the boom and winch of the crane,performing for example processing such as conversion from the requiredelectrical signals to hydraulic signals.

FIG. 3 is a side view showing the external appearance of crane 1employed in the embodiment; as shown in this Figure, it illustrates acondition in which the bottom mechanism is arranged on the ground bymeans of an outrigger 3. At the top of the bottom mechanism, there isfreely rotatably arranged an upper rotary element 2 constituting arevolver frame; a boom 4 is freely rotatably journalled by means of arotary pin on this rotary element 2 such that boom 4 can movevertically.

The hoisting angle α of boom 4 is detected by means of a prescribed boomhoisting angle sensor 10 such as a variable resistor or rotary encodermounted on the rotary pin. Boom 4 is driven by an actuator constitutedby a hydraulic cylinder 5; a detailed description of the construction ofthe boom drive unit that drives boom 4 will be given later.

A wind-up rope 8 provided with a hook 9 at its tip is arranged on boom 4so as to be free to wind up or lower hook 9, by means of a plurality ofguide sheaves including a guide sheave 7 that is arranged at the top ofboom 4. A prescribed suspended load 6 is engaged by hook 9.

The distance between the position 4a of the tip of boom 4 and the centerposition 9a of hook 9 below it is defined as rope length β. Rope lengthβ is detected by a prescribed rope length sensor 11 such as a rotaryencoder that outputs rope length β by detecting rotation of sheave 7.Winding up and lowering of winding-up rope 8 is effected by an actuatorconstituted by hydraulic motor 40 (see FIG. 1); the details of theconstruction of the winch drive unit will be described later. In thisembodiment, working radius X, which is the horizontal distance betweenrotation center 1a of crane 1 and the center position 9a of the hook, istaken as a control variable, and lift Y, which is the vertical distancebetween the ground and the center position 9a of the hook is taken as acontrol variable. If the height yt of the boom tip position 4a is known,lift Y can easily be obtained by adding rope length β to this yt.

Also, in this embodiment, a crane is assumed whereof the length L ofboom 4 can be varied; this boom length L is detected by a boom lengthsensor 12 (see FIG. 1). It may be noted that the present invention couldof course be applied to a crane with a fixed boom length L; in thiscase, the boom length L is known, so there is no need to provide a boomlength sensor 12.

Also, as shown in FIG. 1, on hydraulic cylinder 5 there are arrangedpressure sensors 13, 14 to detect the load F applied to boom 4 and todetect the pressure of the pressurized oil of the oil chamber ofhydraulic cylinder 5. Pressure sensor 13 is a sensor that detects thehead pressure PH of retraction chamber 5a of cylinder 5; pressure sensor14 is a sensor that detects the bottom pressure PB of expansion chamber5b of cylinder 5.

As shown in FIG. 1, the detected values α, β, L and PH, PB of boomhoisting angle sensor 10, rope length sensor 11, boom length sensor 12and pressure sensors 13 and 14 are input to control unit 20.

FIG. 2 is a control block diagram of the control block constituted bysensor unit 15 and control unit 20 shown in FIG. 1; as shown in thisFigure, first of all, the load F acting on boom 4 is calculated anddetected by load detection unit 20 using the outputs PH, PB of pressuresensors 13, 14.

Incidentally, when the flexure of boom 4 changes, working radius Xchanges in response to this change. Likewise, boom tip height yt alsochanges in response to the boom flexure.

It is known that the boom flexure changes with the boom hoisting anglea, boom load F and boom length L as parameters. There is therefore aprescribed correspondence relationship indicated by function f shownbelow between working radius X and these parameters α, F and L.

    X=f(α,F,L)                                           (1)

Likewise, there is a prescribed correspondence relationship indicated byfunction g between the boom tip height yt and the above parameters α, Fand L.

    yt=g(α,F,L)                                          (2)

The correspondence relationship between these parameters α, etc. andworking radius X and the correspondence relationship between theseparameters α, etc and boom tip height yt can be determined beforehand byexperiment or simulation, etc and is stored in prescribed memory in theform of a calculation formula or in the form of a table.

In this way, the current working radius X taking into account theflexure of boom 4 can be calculated from the correspondence relationshipindicated by formula (1) above, and the current boom tip height yttaking into account the flexure of boom 4 can be calculated from thecorrespondence relationship indicated by formula (2) above.

Now boom 4 and the winch are driven by operation of operating levers etcby the operator of crane 1 and a target value Xr of working radius Xcorresponding to such lever operation etc is input to control unit 20and a target value Yr of lift Y is input to the same control unit Yr.

Coordinate conversion section 25 calculates the current working radiusX, which is the value of the function corresponding to function f bysubstituting the detected values α and L of sensors 10 and 12 that arecurrently input, and the calculated value F of load detection section 21into formula (1). In the same way, the current boom tip height yt, whichis the function value corresponding to function g, is calculated bysubstituting the input detected values α and L of sensors 10 and 12, andthe calculated value F of load detection section 21, into formula (2).In addition, the current lift Y is calculated by adding the detectedvalue β of the rope length sensor 11 that is currently input to boom tipheight yt that is thus calculated.

When this is done, the deviation ΔX between the working radius targetvalue Xr that is currently input as operating output of an operatinglever or the like and the current working radius X (feedback value) thatis calculated by coordinate conversion section 25, and this workingradius deviation ΔX is input to deviation coordinate conversion section22.

In the same way, the deviation ΔY between the lift target value Xr thatis currently input as operating output of an operating lever or the likeand the current lift Y (feedback amount) calculated by coordinateconversion section 25 is found and this lift deviation ΔY is input todeviation coordinate conversion section 22.

Deviation coordinate conversion section 22 uses the input working radiusdeviation ΔX, the lift deviation ΔY, the detected value a of boomhoisting angle sensor 10, and the detected value L of boom length sensor12 to calculate the deviation Δα of the boom hoisting anglecorresponding to working radius deviation ΔX, and to calculate thedeviation Δβ of the rope length corresponding to the working radiusdeviation ΔX and lift deviation ΔY.

Boom 4 of crane 1, having a prescribed length L, is rotated withprescribed angular velocity dα/dt, so the velocities dX/dt and dY/dt ofthe tip co-ordinate position of boom 4 can in general be found by theangular velocity dα/dt of the axis of rotation of boom 4, boom length Land the Jacobian matrix. Consequently, the deviation Δα of the boomhoisting angle can be found as follows, using the tip co-ordinateposition deviation ΔX, boom length L and the inverse Jacobian matrix.

    Δα=-(ΔX/(L·sin α))        (3)

In the same way, the rope length deviation Δβ can be found by thefollowing formula (4).

    Db=(ΔX/tan α)+ΔY                         (4)

Deviation coordinate conversion section 22 calculates boom hoistingangle deviation Δα by substituting the currently input deviation ΔX anddetected value a etc into formula (3) above and calculates rope lengthdeviation Δβ by substituting deviation ΔX and detected value a etc thatare currently input into formula (4) above.

In this way, when the boom hoisting angle deviation Δα has beencalculated, this deviation Δα is input to deviation angle controlsection 23 and this deviation angle control section 23 calculates andgenerates a control signal αr such as to make this deviation Δβ zero,and this is then output to the boom control section of drive unit 30.This calculated rope length deviation Δβ is also input to rope lengthcontrol section 24 and this rope length control section 24 calculatesand generates a control signal βr such as to make this deviation Δβzero, and this is output to the winch drive section of drive unit 30.

Control signal αr is processed by a boom drive section that is builtaround a boom hoisting flow rate control valve 34.

First of all, control signal αr is supplied to solenoid 31a ofelectromagnetic proportional pressure control valve 31 for decreasingthe boom hoisting angle or is supplied to solenoid 32a ofelectromagnetic proportional pressure control valve 32 for increasingthe boom hoisting angle. Control valve 31 or 32 is thereby actuated,causing a hydraulic signal of pressure corresponding to the inputelectrical signal ar to be applied to pilot port 34a or 34b of flow ratecontrol valve 34.

Pressurized oil discharged from a charging pump 37 is supplied tocontrol valves 31 and 32.

If now we assume that control signal αr indicates "boom lowering",control valve 31 for lowering is actuated, and flow rate control valve34 is shifted to valve position 34c corresponding to the magnitude ofcontrol signal αr; this causes pressurized oil discharged from hydraulicpump 33 for raising or lowering to be supplied to retraction chamber 5aof hydraulic cylinder 5 with a flow rate corresponding to valve position34c.

As a result, boom 4 is lowered in accordance with control signal αr, anddeviation Δα is made zero.

Also, if control signal αr is indicating "boom raising", in the sameway, the corresponding control valve 32 is actuated, causing flow ratecontrol valve 34 to move to valve position 34d corresponding to themagnitude of control signal αr, with the result that pressurized oildischarged from hydraulic pump 33 for raising and lowering is suppliedto extension chamber 5b of hydraulic cylinder 5 with a flow ratecorresponding to this valve position 34d. As a result, boom 34 is raisedcorresponding to control signal αr, and deviation Δα is made zero.

In contrast, control signal βr is processed by the winch drive section,which is built around winch winding-up or lowering flow rate controlvalve 39. Control signal βr is supplied to solenoid 35a ofelectromagnetic proportional pressure control valve 35 for winding up orsolenoid 36a of like pressure control valve 36 for lowering. By thismeans, control valve 35 or 36 is actuated, causing a hydraulic signal ofpressure corresponding to the input electrical signal br to be suppliedto pilot port 39a or 39b of flow rate control valve 39.

Pressurized oil discharged from charging pump 37 is supplied to controlvalves 35, 36.

If now control signal βr is indicating "winch winding up", control valve34 for winding up is actuated, causing flow rate control valve 39 to bemoved to valve position 39c corresponding to the magnitude of controlsignal βr, with the result that pressurized oil discharged fromhydraulic pump 38 for the winch is supplied to the winding-up rotatingside of hydraulic motor 40, with a flow rate corresponding to valveposition 39c.

As a result, wind-up rope 8 is wound up corresponding to control signalβr, and deviation Δβ is made zero.

If control signal βr is indicating "winch lowering", in the same way,the corresponding control valve 36 is actuated, causing flow ratecontrol valve 39 to be shifted to valve position 39d corresponding tothe magnitude of control signal βr, with the result that pressurized oildischarged from hydraulic pump 38 for the winch is supplied to thelowering rotational side of hydraulic motor 40 with a flow ratecorresponding to valve position 39d.

As a result, wind-up rope 8 is lowered corresponding to control signalβr, and deviation Δβ is made zero.

Operation will now be described for the case where a so-called "groundbreaking" operation is performed, in which for example a suspended load6 at the ground is gradually raised, when the operation is performedvarying lift Y while maintaining the working radius X of crane 1 fixed.

First of all, at the commencement of the ground breaking operation, itis desirable that the hook 9 should be set such that the weight ofsuspended load 6 comes directly under the point pin.

The operator then performs processing, for example by operating astart-control switch, to input working radius X0 at the start of controlto control unit 20 as target value Xr. In contrast, in the case of liftY, the operator would input to control unit 20 a target value Yr thatgradually changes with progress of the ground-breaking operation.

Thereupon, the suspended load gets bigger while load 6 is getting closerto being raised in response to rope 8 being wound up by driving thewinch corresponding to the Y direction instruction Yr. As a result, boom4 gradually flexes, causing working radius X to increase and the lift Yin the calculation to alter.

Working radius X and lift Y that are changing with flexing of boom 4 inthis way are calculated as described above by the coordinate conversionsection 25.

Boom control signal αr and winch control signal βr for target values X0,Yr are thereupon generated by control unit 20, using as feedback valuesthe current values X, Y which are changing with this flexure; thesecontrol signals α, βr are simultaneously output to the boom drivesection and winch drive section of drive unit 30, thereby simultaneouslycontrolling the boom hoisting angle and the rope length.

As a result, a ground breaking operation in which suspended load 6 israised can be carried out in a safe manner while keeping working radiusX at a fixed value X0, without abrupt change of lift Y or causing flowof suspended load 6.

Also, operation can likewise be carried out in a safe way whenperforming an operation in which the load of suspended load 6 is madesmaller while load 6 is still suspended, for example as in the case of araw concrete pouring operation.

The action will now be described wherein conversely, operation isperformed while varying the working radius X and keeping the lift Y ofcrane 1 fixed, for example a horizontal movement operation, in whichsuspended load 6 is displaced in the horizontal direction.

In this case, the operator performs processing, by for example operatinga start-control switch, wherein the lift Y0 on start of control is inputto control unit 20 as target value Yr. On the other hand, in the case ofworking radius X, processing is performed wherein target value Xr thatprogressively changes with progress of the horizontal movement operationis input to control unit 20.

When this is done, boom 4 is driven in accordance with the X directioninstruction Xr, and the load applied to boom 4 fluctuates correspondingto the change in the boom hoisting angle α. This causes the flexure ofboom 4 to gradually change, also changing working radius X and lift Y.

Working radius X and lift Y that change in this way depending on theflexure of boom 4 are calculated as described above by the coordinateconversion section 25.

Thereupon, boom control signal αr and winch control signal βr forachieving target values Xr and Y0 are generated by control unit 20,using as feedback quantities the current values X, Y, which are changingwith the flexure amount, and these are simultaneously output to the boomdrive section and winch drive section of drive unit 30, so that the boomhoisting angle and rope length are simultaneously controlled.

As a result, an operation of horizontal displacement in which suspendedload 6 is displaced horizontally while maintaining lift Y at a fixedvalue Y0 can be performed safely.

INDUSTRIAL APPLICABILITY

As described above, with the present invention, the boom hoisting angleand the rope length can be controlled concurrently, using as feedbackquantities the working radius and lift taking into account the currentflexure of the boom, so an operation which advances by changing the liftwhile keeping the working radius at a fixed value or an operation whichadvances by changing the working radius while keeping the lift at afixed value can be performed in a safe manner.

We claim:
 1. Crane control device comprising:boom drive means forchanging a boom hoisting angle in response to an input driveinstruction; winch drive means for changing a rope length of the wind-uprope from a tip of the boom to a hook in response to the input driveinstruction; boom hoisting angle detection means for detecting the boomhoisting angle; rope length detection means for detecting the ropelength; boom load detection means for detecting a load acting on theboom; setting means for setting beforehand, taking the boom hoistingangle, boom load and boom length as parameters, a first correspondencerelationship of these parameters and the working radius, and a secondcorrespondence relationship of the parameters and the boom tip verticalposition; first calculating means for calculating a current workingradius based on the detected values of the boom hoisting angle detectionmeans and the boom load detection means, the value of the boom lengthand the first correspondence relationship that is set in the settingmeans, and for calculating a current lift based on a current boom tipvertical position and the detected value of the rope length detectionmeans, the current boom tip vertical position being obtained based onthe detected values of the boom hoisting angle detection means and theboom load detection means, the value of the boom length and the secondcorrespondence relationship set in the setting means; and control meansfor outputting drive instructions respectively to the boom drive meansand winch drive means such as to perform a prescribed operation whereinthe lift, indicating the vertical distance from the ground to the hookis varied while maintaining the working radius, indicating thehorizontal distance from the rotation center of the crane to the boomtip at a fixed value, while inputting as feedback quantities the currentworking radius and the current lift calculated by the first calculatingmeans.
 2. Crane control device according to claim 1, comprising:inputmeans for inputting a target value of the working radius and a targetvalue of the lift; second calculating means for calculating a boomhoisting angle deviation corresponding to a working radius deviationbased on the working radius deviation, detected value of the boomhoisting angle detection means and the value of the boom length byobtaining the deviation of a working radius target value input by theinput means and a current working radius calculated by the firstcalculating means, and for calculating a rope length deviationcorresponding to the working radius deviation and the lift deviationbased on the lift deviation, the working radius deviation and thedetected values of the boom hoisting angle detection means by obtainingdeviation between a lift target value that is input by the input meansand current lift calculated by the first calculating means; and controlmeans for outputting a drive instruction to the boom drive means such asto make the boom hoisting angle deviation calculated by the secondcalculating means zero and to the winch drive means such as to make therope length deviation calculated by the second calculating means zero.3. Crane control device comprising:boom drive means for changing theboom hoisting angle in response to an input drive instruction; winchdrive means for changing the rope length of the wind-up rope from theboom tip to the hook in response to an input drive instruction; boomhoisting angle detection means for detecting the boom hoisting angle;rope length detection means for detecting the rope length; boom loaddetection means for detecting a load acting on the boom; setting meansfor setting beforehand, taking the boom hoisting angle, boom load andboom length as parameters, a first correspondence relationship of theseparameters and the working radius, and a second correspondencerelationship of the parameters and the boom tip vertical position; firstcalculating means for calculating a current working radius based on thedetected values of the boom hoisting angle detection means and the boomload detection means, the value of the boom length and the firstcorrespondence relationship that is set in the setting means, and forcalculating a current lift based on a current boom tip vertical positionand the detected value of the rope length detection means, the currentboom tip vertical position being obtained based on the detected valuesof the boom hoisting angle detection means and the boom load detectionmeans, the value of the boom length and the second correspondencerelationship set in the setting means; and control means for outputtingdrive instructions respectively to the boom drive means and winch drivemeans such as to perform a prescribed operation by varying the workingradius indicating the horizontal distance from the rotation center ofthe crane to the boom tip while maintaining the lift indicating thevertical distance from the ground to the hook at a fixed value, whileinputting as feedback quantities the current working radius and thecurrent lift calculated by the first calculating means.
 4. Crane controldevice according to claim 3, comprising:input means for inputting atarget value of the working radius and a target value of the lift;second calculating means for calculating a boom hoisting angle deviationcorresponding to a working radius deviation based on the working radiusdeviation, detected value of the boom hoisting angle detection means andthe value of the boom length by obtaining the deviation of a workingradius target value input by the input means and a current workingradius calculated by the first calculating means, and for calculating arope length deviation corresponding to the working radius deviation andthe lift deviation based on the lift deviation, the working radiusdeviation and the detected values of the boom hoisting angle detectionmeans by obtaining deviation between a lift target value that is inputby the input means and current lift calculated by the first calculatingmeans; control means for outputting a drive instruction to the boomdrive means such as to make the boom hoisting angle deviation calculatedby the second calculating means zero and to the winch drive means suchas to make the rope length deviation calculated by the secondcalculating means zero.